Hold Up Half the Sky
by Whiscash
Summary: For most of Alphys' life, the stars had been - much like her love life - entirely theoretical. But one of the things about theories is that sometimes they end up being totally, completely, 100% oh-my-god-what-is-my-life-even wrong. (post-pacifist ending Alphyne fluff)


**Hold Up Half the Sky**

 **by Whiscash**

 **pairing:** Alphys/Undyne

 **notes:**...welp. So I have no idea what it is about monsters kissing that apparently makes me more prolific (by my standards lol) than I have been in like, ever...? but okay – same fluff, different OTP! XD Prompt this time was "stargazing" - as always, if you have any thoughts on how I did with these two I would love to hear them! Thank you for reading c:

* * *

For most of Alphys' life, the stars had been – much like her love life – entirely theoretical.

She knew they _existed_ , for sure, and she could gather enough data to make reasonable predictions about them – where and when they should be visible, and depending on variables, what they ought to look like based on her calculations. She'd read about them in old books about the surface, and seen them plenty of times in anime, although obviously that came with a bit of, um, artistic license. But no matter how much research she did, at the end of the day she wasn't any closer than any other monster to knowing what it actually _felt_ like, to look up at the stars. All Alphys could do, like everyone else, was imagine, gazing up at the cold, empty ceilings of the lab and trying to picture a velvet sky instead, stars like echo flowers (that was the closest thing she had for visual reference. Alphys had never liked echo flowers much, though – there was something unsettling about hearing her own voice, trapped in stasis until her words were passed to the next person. And, okay, maybe she just really hated the sound of her own voice) mapping out a world of possibilities, a world so much bigger than anything she'd ever known – where, one day, they could all escape.

That was the theory, anyway, and Alphys' theories were pretty important – she _was_ the Royal Scientist, after all (emphasis on 'was'), and that meant Asgore was counting on her to figure it all out, to come up with solutions to problems they hadn't even encountered yet. And she desperately didn't want to let him down – to let _everyone_ down – but sometimes, it felt like she was in way over her head. She was supposed to be so smart, to have all the answers, just like...well, like any Royal Scientist ought to. But even _before_ everything started to go wrong, Alphys had always had the creeping dread that theories weren't enough, that _she_ wasn't enough. It felt, sometimes, like she spent her whole life theorising and planning and obsessing about things she would never, ever get to experience for herself – and most of them had nothing to do with the surface.

Like that whole Asgore... _thing_ she'd been trying to convince herself was totally just professional admiration, because oh my god, Alphys, he was the _king_ , and her boss, and technically he was still married even if no one had seen the queen in years, and even if he hadn't been, the idea that _she_ could ever...Again, theoretically, Alphys had an idea of how dating was supposed to work – you found someone you liked, and then you kept giving them presents and compliments until you raised their affection high enough to ask them out, and was a cutscene and...you won, or something? But obviously, life wasn't a dating sim – for one thing, in the games, Alphys wasn't a literal trashbag who dissolved into a blushing, stuttering wreck the moment anyone vaguely attractive so much as glanced in her direction, so. That kind of put her at a disadvantage with the whole actual-life dating thing.

But that was fine! It wasn't like Alphys even had any _time_ for dating, because even if she had zero chance with Asgore like _that_ , he still respected her. He trusted her with maybe the most important research ever conducted in the Underground – that was how he'd said it – and that was why everything had to be fine, even when it was the complete opposite. Everything was _fine_ , she'd tell him, day after day – the experiments were producing some, um, interesting _results_ , but no, there was no reason at all for him to come all the way out to the lab just to check up on her, she was sure he had better things to do! She'd have the data back for him soon, she promised, and some days she even came close to convincing herself that maybe it would be okay, that if she just stayed focused and didn't panic – ha, cause she was so good at _that_ – she'd be able to figure out some way to...to stop everything from falling apart, both metaphorically and literally.

It was probably around then Alphys started to realise the other thing about theories – that sometimes they ended up being totally, completely, 100% oh-my-god-what-is-my-life-even wrong.

Because out of all the thousands of possible outcomes she'd drawn up where they managed to break the barrier – ones where Asgore freed them all, where he absorbed the souls and finally wreaked his revenge on the humans, or the (statistically more likely) ones where the humans took everything from them again – none of them could have prepared Alphys for how it felt to look up at the stars for the first time.

And she was pretty sure there was no theory or equation or dating sim in _existence_ that should have ended with her sitting on the beach at night under the stars, pointing out the constellations in the flesh – well, gas – with her ridiculously cool and beautiful and amazing in every conceivable way _girlfriend_. Because _that_! Was a thing that had happened!('?!' was the sum of Alphys' very scientific conclusions on the matter.) Alphys was just grateful she was just about holding in the constant internal screaming whenever Undyne looked at her or smiled or just generally existed in her vicinity, even now as she sat with her arm casually draped over Alphys' shoulder as they pored over the constellations in her guidebook.

"So where's _this_ one?" Undyne asked, her vibrant hair briefly tickling Alphys' snout as she tapped a finger against the guide.

"Oh, that's _Apus_ – it means, um, 'bird of paradise'? But it's not always visible around this time of the year. Depending on the – the weather conditions." Alphys glanced up, grinning as she caught Undyne's visible eye. "F-funny how now we actually _have_ weather for you to ask me about, huh?"

"Hey, there _could_ have been weather back in the Underground!" Undyne protested. "What if...what if the sun suddenly crashed into us one day, threatening to burn up everything and everyone we knew and loved? How would I have known when to show up and how hard I needed to punch it in the face _then_?!"

She clenched her fist dramatically, and Alphys giggled, totally not admiring the shape of her muscles under her scales or anything. "I, um, I don't think it works like that. Or that the sun actually _has_ a face you can punch."

Undyne shrugged. "Whatever you say, nerd," she said affectionately, and planted a loud, wet kiss on Alphys' cheek, making her yellow scales immediately flame scarlet. Undyne grinned wickedly, a flash of sharp teeth in the moonlight as Alphys struggled to remember how to words, and pulled her closer, resting her chin on top of Alphys' head. "It's still pretty cool. From what you used to tell me about humans, I always pictured these awesome laser beams shooting from the stars – _that_ had to be what made the humans so powerful, right? Their greatest weapon against us?"

"Oh – you mean like in Seafarer Star? But, see, it's not actually about the stars," Alphys explained. "It's when they express their truest self – when it seems like all hope is lost but then the light of courage, perseverance, kindness, _love_ burns bright within them and calls out to the guardians of the sky. And that's when they look up to the stars and feel the spirit of the constellations flowing through them and only _then_ do they unleash their true power – when they realise how far they've come and the friendships they've made and the true purpose of their destiny and who they really are inside so the power that was inside them all along shines through in its purest form and...and...yeah," she finished lamely, feeling her blush creeping back as she realised just how long and how quickly she'd been babbling on, oh god, Undyne was probably thinking she's _such a loser_ right now...

"Yeah, yeah!" But she was nodding along eagerly, like she was totally enthralled by Alphys' rambling feels about magical girls. "That's it – so the bigger their heart or friendship power or whatever, the cooler their sword or gun or magical light cannon of ultimate destruction. Man, that was _awesome_. Can you imagine if it happened like that for us too?!"

Undyne looked up at the sky, starlight shining in her eye and a dreamy smile on her face as she was probably imagining wielding some kind of insane ultra-hyper-mega-death spear of doom – Alphys had hardly ever seen her look so relaxed, so content, so _happy_ , and out of nowhere she felt an unmistakable pang of guilt, sharp as Undyne's teeth. "Y-yeah, I can imagine."

That was an understatement – Alphys had imagined _a lot_ , down to the tiniest ridiculously specific detail. That had always been her escape, all those endless days and nights in the lab when _everything was so wrong_ , recasting herself as a plucky shojo heroine. Her crippling anxiety and social awkwardness would be somehow quirky and adorable, and inexplicably be the source of her true strength instead of ensuring that she managed to screw up everything that might ever have been good in her life. Cute boys and girls would actually want to date her, her problems would always be solved in twenty minutes – forty, maybe, for a season finale – and even when she messed up, everything would turn out okay because she'd always have her friends, with their crazy yet perfectly complementary personalities and skill sets, and together they could achieve anything. She wouldn't have to face her failures every day, watching the letters piling up with that awful sinking feeling in her stomach until she curled up under her duvet, hot, shameful tears trickling down her face as she thought about opening them and knew, yet again, that she couldn't, she wasn't strong enough. These monsters needed everything, they _deserved_ everything, and Alphys was...Alphys was _nothing_.

That thought settled in her mind like a stone, unmoving no matter how hard she tried to push it away – because those days were so far away now, she'd told everyone the truth and she couldn't undo the experiments, but she'd tried her best with the families and done everything she could to make it right, hadn't she? But even here, with Undyne – _especially_ here with Undyne – the guilt kept gnawing at the corners of her mind, and – maybe she'd regret saying it, but she also knew she'd never be able to stop thinking about it if she _didn't_ say it.

Alphys took a deep breath, psyching herself up.

"Undyne..."

"Yeah?"

"I'm – I'm sorry."

"Huh?" Undyne snapped to attention, her ponytail swinging as she cocked her head to look back at Alphys. "For what?"

"F-for making you think anime was real." Alphys tried to force a smile – it sounded so dumb, after all, but she could only manage an awkward kind of grimace. "I...I let you believe something that wasn't true, just because I wanted you to think _I_ was this – this cool Royal Scientist who knew about human history, who could actually be _useful_ to you, not some dorky loser scavenging cartoons from the dump. I thought you'd n-never want to be friends if you knew what I was really like, s-so – I lied, to you, to Asgore, t-to pretty much everyone, about everything, huh?" She let out an weak, pathetic little laugh as though that could somehow stop her voice from shaking, hold back the tears she had to furiously blink back because everything had been going so well, they were having such a lovely evening and then she had to go start _thinking_ and open her big dumb mouth _what was wrong with her?_ "I-I should have told you the truth a long time ago, and then maybe...I was just so scared you'd never talk to me again – b-but maybe that's what you should've done. I guess it's what I deserved, after everything..."

"Alphys," Undyne interrupted her, and Alphys' heart plummeted as she felt her shift away for a moment before her hand returned, gently but firmly lifting her chin and forcing Alphys to look at her. Her expression was uncharacteristically sombre, piercing, yellow eye seeming to stare straight into Alphys' soul – until she let out a loud scoff, shaking her head. "Seriously – you think _that's_ what I care about? That anime isn't real?"

Alphys fidgeted with her claws. "W-well, I..."

"Listen," Undyne cut her off again, but her voice was gentle, like Alphys had hardly ever heard it before. "Anime's awesome. I love me some big swords, giant robots, magical girls. But you know what's like over 9000 times better than all that stuff put together? This." She lifted her arm from around Alphys' shoulders to make a dramatic sweeping gesture, stretching as far as she could to indicate the beach, the ocean, the stars, the surface. "Alphy, _this_ is real. This is what I've been fighting for my whole life – ever since I was a little squirt, all I ever wanted was to be the one to free our people. I always believed that if I just worked hard enough, trained to be the strongest I could be and fought my way to the top of the Royal Guard, I could take on anything, all of the humans by myself if I had to. I promised everyone – I _had_ to keep believing in that, to have something to fight for every day. It was never about what was on the surface – it was about our freedom! Justice! _Vengeance_!" Her fist clenched reflexively around an imaginary spear as her voice rose to a more typical Undyne-volume, but then she grabbed Alphys' clasped hands instead, squeezing them as a familiar determination sparkled in her eye and a broad, bright grin lit up her face. "For real – you think I hung out with you because I cared about any of that nerdy science stuff? I liked _you_ – the way you explain things, all your ideas and _passion_ , how cute you are when you get all starry-eyed and gushy about...anything, it doesn't matter. I don't care if the history was real – _you're_ real, Alphy. You made this happen for me – for all of us."

"B-but...I..." It was almost too much, too good – Alphys didn't _deserve_ this, she thought, and part of her wanted to duck her head and hide from Undyne's unrelenting gaze, cower away in the shame – but the rest just wanted to hold onto her forever, never letting go even if the tightness of her grip _was_ a little painful. "But I didn't do anything – it was Frisk who freed us?"

"Yeah, yeah, I know Frisk broke the barrier because of determination or whatever – that's your area, not mine – but they'd never have made it that far if it wasn't for you. I was..." Undyne hesitated, and wow, she was actually _blushing_ , cheeks flushing a deeper shade of navy. "Look, as soon I heard there was a human, I didn't think about – I didn't think, period. I was just gonna get that soul, no matter what it took. Even after they refused to fight me, I just thought – what's _one_ human life in exchange for our freedom, after everything they've taken from us? But I was..." she bit her lip, glancing down at their clasped hands instead of Alphys' eyes, " _wrong_. If it wasn't for you and Papyrus, Frisk would be – they wouldn't have made it, and that would have screwed us all. But you helped them, and you helped _me_ realise they could be a friend too. Plus," she added, smirking, "you gotta admit, you made things a hell of a lot more interesting for them down there. If the whole Royal Guard being out for their blood wasn't enough."

Alphys couldn't help but let out a little snort at that, even if it was terrible of her. "Heh...yeah. I guess I did do _that_."

She honestly hadn't _meant_ to watch Frisk as long as she did – just long enough to assess the threat and report back to Asgore – but there was something so...charming about them. She found herself really rooting for them as they progressed, met new monsters, made friends, never gave up through even the most gruelling battles – it was a super satisfying character arc, except you know, _actually happening_. Which meant she could be part of it! But she couldn't exactly pop up out of nowhere and be all "hi I've been secretly watching you and I think you're really cool can we be friends?" – there had to be an actual _reason_ Frisk needed her help. Like...a killer robot.

Okay, so the whole thing was kind of messed up and weird and it all escalated _way_ more quickly than Alphys was expecting, but. In a weird way, maybe Undyne was right? She had helped Frisk, even if she'd set a lot of the danger up herself, but the really incredible thing was – they were still there at the end, when she'd finally told them the truth. They listened and they told her they still wanted to be friends, that she was a good person, that they _believed_ in her just like she had in them, and Alphys wanted with all her heart to see them make it to the end...whatever their end ended up being, even if it wasn't the one Asgore wanted, the one they were all dreaming of. And it ended up being so much more than anything she'd imagined, even better than the Mew Mew season one finale – Frisk succeeded with the power of the friendships they'd made along the way, and Alphys was _part of that_. Huh, now she thought about it, that seemed familiar somehow...

"Damn right you did," Undyne said proudly, startling Alphys out of her musings as she pulled her into a kind of noogie/nuzzle combo, aggressively rubbing her chin against the top of Alphys' head with one arm around her neck. "So! I don't _ever_ wanna hear you talking trash about my totally amazing, badass, adorable girlfriend again, 'kay?!"

Alphys laughed, struggling ineffectively as though she wouldn't be happy to have Undyne's face permanently attached to hers, if that were at all feasible or ethical. "Okay, okay, I'll shut up now."

"Thought so." Undyne seemed satisfied with that as she turned her attention back to the sky, releasing Alphys from her grip to point at a cluster of stars almost right above them, twinkling out over the sea. "So, anyway – what cool powers do you think we'd get from that one?"

"That's..." Alphys flicked through the pages of her book. "The Big Dipper. Composed of the seven brightest stars of the Ursa Major."

"Like a roller coaster?" Undyne tapped a finger thoughtfully against her chin. "What's that represent – the power to make your enemies throw up?"

"Oh my god, yeah – gross," Alphys snorted, wrinkling her snout as she remembered that ill-fated trip to the theme park. Poor Papyrus – he never had a chance when Undyne triple-dared him to go on the Hyper Loop Wipeout. They'd tried to take his mind off it by checking out the theatre, but were kicked out after Mettaton took it upon himself to inject the show with "a little more _pizzazz_ , my darlings". Alphys had no idea _where_ he kept getting all those rose petals from, but they didn't seem to go down so well as they used to in the Underground. "Though I guess it could be useful if you had to, I dunno, stop someone from talking?"

"Punching them works pretty well for that, too," Undyne said, a little too cheerfully, until Alphys narrowed her eyes at her in as disapproving a look as she could manage, and she groaned, rolling her eye. "Ugh, _fine_. But not every problem can be solved by punching or stabbing or yelling at things. _Most_ things, but not everything – like finally freeing your people, getting humans to stop running away from you, and making tapioca pudding. Happy now?"

Alphys grinned – she was so cute when she went all tsundre like that – and snuggled back against Undyne, daring to press a kiss to her gills as a reward. "H-happier than I've ever been, yup."

Undyne rested her head against Alphys' and they were quiet for a few moments, comfortable under the blanket of the night with the sound of the waves breaking on the shore. Then she said: "Y'know, you'd look _really_ cute in a Seafarer Star outfit."

"Ahhh! Oh god...r-really?" Alphys squeaked, pressing her claws to her cheeks to unsuccessfully hide her blush. "You think? I mean, they're so... _revealing_."

" _Yeah_ they are." Undyne winked at her, tongue darting out to lick her lips suggestively, and wow that was _so far beyond okay_ what she was doing to Alphys right now, blushing so hard her glasses were steaming up as her mind helpfully started to fill with scenarios that were definitely not PG-13.

"Well...people do do that, sometimes," she said, trying to sound casual, like she hadn't secretly been planning her Seafarer Star cosplay since she finished the series. That was all just in theory too, of course – it wasn't like she'd ever have the guts to _wear_ something like that in the Underground, even if she had any place to wear it to. "Dress up like Seafarer Star – pretty much any anime character actually. They make these incredible outfits – even all the weapons! Safe versions, obviously."

Undyne's face lit up, and Alphys knew she'd had her at "weapons". " _Seriously_? Where? When can we go?! I'm sure Papy would come with us, and Frisk. And I guess...we should probably ask Mettaton, too." She wrinkled where her nose would have been, if she'd had one – Alphys knew those two didn't often see eye-to-eye, or eye-to-expression-panel, but she appreciated that Undyne was trying, sort of.

"He'll probably demand a whole redesign when he sees all those sparkles," Alphys sighed, but she already felt a flutter of excitement in her stomach at the thought that this could actually _happen_ , now. It'd be terrifying, too, but she'd be with Undyne and the others, and she had so many ideas for making Star's light cannon... "B-but yes! We should definitely go! I've wanted to for, well, forever – but! I'm only cosplaying – I mean, dressing up for it if _you_ will too." If she had an opportunity to get Undyne in a super short magical-girl skirt, _heck_ yeah she was going to take it.

"Me?" Undyne arched an eyebrow, considering the possibility for a second before she grinned, flashing all her teeth in an ever-so-slightly predatory manner, and Alphys was a little alarmed by how into it she was. "Sure! You're _on_! I could be the Guardian of Shadows, determined to capture Seafarer Star, learn the secrets of her powers...and _ravish_ her."

"Ummm, _what_ ," Alphys spluttered – that was _not_ the response she'd anticipated from Undyne, although the image of her girlfriend wearing a tux and long, flowing cape, looming over her all dark and menacing...that presented a whole other, um...very intriguing scientific hypothesis. One that would definitely require further exploration. "Th-that last part is _not_ canon! That means it never happens in the show," she explained hastily, in a futile attempt to regain what little composure she ever had.

Undyne just chuckled, deep and throaty and nope, that was it, Alphys was _gone_. "Maybe not yet, but it happens _plenty_ on the internet. I mean, it doesn't take a genius to figure that one out. Am I right, Alphy?"

Any other time, Alphys might have gone into a whole thing about how she got why people shipped it, but honestly it would make _zero_ sense for Star's character arc and she was so over that whole "redeemed by love" trope, but her brain had kind of short-circuited long ago with Undyne looking at her like...like _that_ , a suggestive smirk playing on her lips and a familiar, dangerous gleam in her eye – and before she had a chance to respond, she pounced, wrestling Alphys to the floor and smothering every part of her she could reach – her cheeks, her forehead, her snout, her neck – in kisses as she giggled helplessly, powerless to escape even if she wanted to (and _why would she ever want to?_ ).

"Man, _screw_ anime," she said fiercely, but her expression was as tender as her words were controversial, finally ceasing her onslaught long enough for Alphys to catch her breath. "This is better. This is everything – why would I even care about light cannons and giant swords when I get to have _you_ , Alphy?"

Alphys was pretty sure the words didn't exist to describe the desire, gratitude, love, _everything_ she could feel pulsing through her soul, her whole body trembling from Undyne's touch and Undyne's voice and _Undyne_ , gazing down at her like she was amazing, like she _was_ a magical girl – so she reached up, pressing their lips together in a clumsy but passionate kiss. Undyne's strong arms circled around her, stroking down Alphys' back and holding her close as she deepened the kiss, and for a few brief, brilliant moments, the rest of the world faded away – there were no more thoughts, no more history. Just the two of them, under the stars, and nothing else mattered.

"C-c-can we, um," she mumbled against Undyne's lips when they broke the kiss, her eyes closed as they rested their foreheads together because she actually saying this to _Undyne_ , not to her computer screen, "can we maybe...go somewhere more private? I – I'm getting sand between my scales."

Alphys mentally facepalmed as soon as she'd gotten the words out, because wow, _smooth_ – but Undyne just smiled knowingly and nodded.

"I thought you'd _never_ ask." She rose to her feet in one enviably smooth, fluid motion, leaving Alphys sprawled inelegantly on the sand like a turtle on its back. Undyne held out a hand to help her up, but when she took it, simply scooped her straight up into a bridal carry as Alphys let out a yelp in equal parts surprise and delight.

"You're not going to throw me in the sea again, are you?" she asked. That had become one of Undyne's new favourite pastimes, along with Papyrus, Frisk, Sans...one time even Mettaton, almost, until Alphys had managed to stop her because robots and water _did not mix_.

Undyne snorted, not even breaking a sweat as she carried Alphys across the beach and back towards the town. "Babe, I could freakin' _juggle_ you if I wanted to." She laughed at Alphys' alarmed expression. "But I won't, don't worry! Gotta have my girl back in one piece."

Alphys did her best to stifle the embarrassing high-pitched squee she almost let out at _her girl_ , and let herself relax, resting her head in the crook of Undyne's neck. From here, the stars looked even brighter, a scattered, twinkling path guiding them back towards the lights of the city, and much clearer than Alphys thought they should have been under the conditions.

But that was the thing about theories – they didn't always reflect reality. Sometimes your calculations were way off, sometimes everything went disastrously wrong, and sometimes – okay, _this_ time – you ended up in the arms of the most amazing girl on the planet, and it was better than than literally anything you ever dreamed your life could be. Which also meant that – theoretically – everything just might turn out to be okay in the end, after all. Even after all the times she'd thought nothing would ever be okay again.

Alphys didn't know for sure exactly what she was going to discover in the data – but she was sure looking forward to testing this one out.


End file.
